Steam turbine nozzle segment having arcuate interface

ABSTRACT

Steam turbine nozzle segments with conical interfaces are disclosed. In one embodiment a steam turbine static nozzle blade includes: an airfoil; an inner sidewall integral with a first side of the airfoil; and an outer sidewall integral with a second side of the airfoil; the inner sidewall and the outer sidewall each including: a pressure side having an arcuate concave surface extending substantially an entire length of the sidewall; and a suction side having an arcuate convex surface extending substantially the entire length of the sidewall.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a steam turbine nozzleassembly, or diaphragm stage. Specifically, the subject matter disclosedherein relates to a steam turbine nozzle assembly including a pluralityof nozzle segments with arcuate or “conical” (e.g., arced concave, arcedconvex) interfaces.

Steam turbines include static nozzle (or “airfoil”) segments that directflow of a working fluid into turbine buckets connected to a rotatingrotor. A complete assembly of nozzle segments is commonly referred to asa diaphragm stage of the steam turbine. One method of constructing thediaphragm stage is to weld (or alternatively, braze) a plurality ofsingle airfoils with integrated sidewalls (“static nozzle blades”, or“singlets”) to inner and outer rings. Each of these singlets haveinterfaces to which adjacent singlets are welded or brazed (in the innerand outer ring). These interfaces include an axial leading edge section(or “pressure-side” section) oriented parallel to the steam turbine'saxis, and an angled trailing edge section (or “suction-side” section).While the current singlet design including angled interface sectionsallows for a tight fit between individual segments, the angledinterfaces make removal and repair of individual segments nearlyimpossible.

BRIEF DESCRIPTION OF THE INVENTION

Steam turbine nozzle segments with conical interfaces are disclosed. Inone embodiment a steam turbine static nozzle blade includes: an airfoil;an inner sidewall integral with a first side of the airfoil; and anouter sidewall integral with a second side of the airfoil; the innersidewall and the outer sidewall each including: a pressure side havingan arcuate concave surface extending substantially an entire length ofthe sidewall; and a suction side having an arcuate convex surfaceextending substantially the entire length of the sidewall.

A first aspect of the invention includes a steam turbine static nozzleblade comprising: an airfoil; an inner sidewall integral with a firstside of the airfoil; and an outer sidewall integral with a second sideof the airfoil; the inner sidewall and the outer sidewall eachincluding: a pressure side having an arcuate concave surface extendingsubstantially an entire length of the sidewall; and a suction sidehaving an arcuate convex surface extending substantially the entirelength of the sidewall.

A second aspect of the invention includes a steam turbine diaphragmassembly comprising: an outer diaphragm ring; an inner diaphragm ring;and an annulus of static nozzle blades between the inner diaphragm ringand the outer diaphragm ring, each static nozzle blade comprising: anairfoil; an inner sidewall integral with a first side of the airfoil;and an outer sidewall integral with a second side of the airfoil; theinner sidewall and the outer sidewall each including: a pressure sidehaving an arcuate concave surface extending substantially an entirelength of the sidewall; and a suction side having an arcuate convexsurface extending substantially the entire length of the sidewall;wherein at least one of the static nozzle blades is demountably attachedto a second one of the static nozzle blades.

A third aspect of the invention includes a steam turbine diaphragmassembly comprising: an outer diaphragm ring; an inner diaphragm ring;and an annulus of static nozzle blades between the inner diaphragm ringand the outer diaphragm ring, each static nozzle blade comprising: anairfoil; an inner sidewall integral with a first side of the airfoil;and an outer sidewall integral with a second side of the airfoil; theinner sidewall and the outer sidewall each including: a pressure sidehaving an arcuate concave surface extending substantially an entirelength of the sidewall; and a suction side having an arcuate convexsurface extending substantially the entire length of the sidewall,wherein at least one of the static nozzle blades is demountably attachedto a second one of the static nozzle blades in an axial direction; and aplurality of removable weld joints, each removable weld jointsubstantially removably affixing one of the static nozzle blades to oneof the outer diaphragm ring or the inner diaphragm ring.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a plan view of a top of a steam turbine nozzle assembly.

FIG. 2 shows a three-dimensional perspective views of a steam turbinenozzle assembly.

FIG. 3 shows a partial three-dimensional perspective view of a steamturbine diaphragm assembly.

FIG. 4 shows a three-dimensional perspective view of a steam turbinestatic nozzle blade according to an embodiment.

FIGS. 5-6 show three-dimensional perspective views of a plurality ofsteam turbine static nozzle blades according to embodiments.

FIG. 7 shows a partial three-dimensional perspective view of a steamturbine diaphragm assembly according to an embodiment.

It is noted that the drawings of the invention are not to scale. Thedrawings are intended to depict only typical aspects of the invention,and therefore should not be considered as limiting the scope of theinvention. In the drawings, like numbering represents like elementsbetween the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, aspects of the invention provide for a steam turbinenozzle segment having a conical interface. Specifically, aspects of theinvention provide for a steam turbine nozzle assembly including aplurality of nozzle segments with arcuate or “conical” (e.g., arcedconcave, arced convex) interfaces. These arced interfaces may allow forremoval and/or repair of individual nozzle segments while substantiallymaintaining the structural integrity of the nozzle assembly.

Referring to the drawings, FIGS. 1-2 show a nozzle assembly 100 for asteam turbine (not shown). FIG. 1 shows a plan view of nozzle assembly100, while FIG. 2 shows a three-dimensional schematic of nozzle assembly100. Nozzle assembly 100 includes a static nozzle blade 10 including atleast one airfoil 12 having an inner sidewall 14 and an outer sidewall16. Nozzle assembly 100 further includes an inner ring 18 and an outerring 20. Inner and outer, as used herein, refer to a radial positionrelative to a rotor (not shown) to which an inner end of airfoil 12 iscoupled via inner ring 18. Inner ring 18 and inner sidewall 14 (andsimilarly, outer ring 20 and outer sidewall 16) are coupled together atan interface 80, which is understood to refer to the entire area wherethe rings and sidewall are adjacent and coupled. Inner ring 18 and innersidewall 14 (and similarly, outer ring 20 and outer sidewall 16) arewelded (or alternatively, brazed) together at several points atinterface 80 (FIG. 1). It is understood that as described herein,brazing may be performed as an alternative to welding. As is understoodin the art, welding and brazing may be used to join metals together. Asis further understood in the art, welding may be performed by meltingand fusing metals together, usually by adding a filler material.Brazing, by contrast, usually does not involve melting the base metalsbeing joined, and is usually performed at lower temperatures thanwelding. While metal joints are described herein as “weld joints”, it isunderstood that these metal joints may alternatively be described as“braze joints.”

Returning to FIG. 1, the multiple welded areas of interfaces 80, on bothan entrance (front) side of airfoil 12 and an exit (back) side ofairfoil 12, that are welded together are shown generally as weld joints90 in FIGS. 1 and 2. Interfaces 80 between rings 18, 20 and sidewalls14, 16 may each include a mechanical radial stop 19 which maintainsairfoil 12 in the correct radial position during welding and preventsweld shrinkage. Interfaces 80 each may further include a mechanicalaxial stop 17 which maintains airfoil 12 in the correct axial positionand controls the weld length depth. These mechanical stops 17, 19comprise an interconnection of a series of male steps which engage incorresponding female steps of the complementary part as described inmore detail herein.

Turning to FIG. 3, the nozzle assembly 100 of FIG. 2 is shown, furtherincluding a plurality of static nozzle blades 10 arranged in a portionof a diaphragm assembly (full assembly omitted for clarity). As shown,sidewalls 14, 16 of static nozzle blades 10 may include angledinterfaces 34 (e.g., a “dogleg” interface including two surfacesoriented at obtuse angles). These angled interfaces 34 may allow for aplurality of static nozzle blades to be arranged substantially flushwith one another in nozzle assembly 100. As shown, the plurality ofstatic nozzle blades 10 are held within inner 18 and outer sidewalls 20via the plurality of welds 90.

Turning to FIG. 4, a steam turbine static nozzle blade 110 is shownaccording to an embodiment. Static nozzle blade 110 may include anairfoil 112, an inner sidewall 114, and an outer sidewall 116. As shown,inner sidewall 114 may be integral with a first side of the airfoil 112(e.g., via machining from a forging or block, welding, casting, brazing,etc.), and outer sidewall 116 may be integral with a second side of theairfoil 112 (e.g., via machining from a forging or block, welding,casting, brazing, etc.). The inner sidewall 114 and the outer sidewall116 may each include a pressure side 124 and a suction side 126. Theterms “pressure side” and “suction side” correspond to the pressure sideand suction side of airfoil 112, respectively. As is known in the art,the pressure side of airfoil 112 is the high-pressure side designed toguide the flow of a working fluid through the static nozzle blade 110.As is further known in the art, the suction side of airfoil 112 is thelower-pressure side substantially opposing the pressure side. Eachpressure side 124 may have an arcuate concave surface 134, and eachsuction side 126 may have an arcuate convex surface 136. In oneembodiment, the arcuate concave surface 134 may extend substantially anentire length L of the sidewall 114, 116, respectively, and the arcuateconvex surface 136 may extend substantially the entire length L of thesidewall 114, 116, respectively. In one embodiment, the arcuate concavesurface 134 of the inner sidewall 114 has a substantially equal arcradius to the arcuate convex surface 136 of the inner sidewall 114.Further, in this embodiment, the arcuate concave surface 134 of theouter sidewall 116 and the arcuate convex surface 136 of the outersidewall 116 may have a substantially equal arc radius. Additionally, inthis embodiment, the arcuate concave surfaces 134 of the inner sidewall114 and outer sidewall 116, respectively, may have substantially equalarc lengths as the arcuate convex surfaces 136 of the inner sidewall 114and outer sidewall 116, respectively.

With continuing reference to FIG. 4, in one embodiment, the arcuateconcave surface 134 of the inner sidewall 114 and the arcuate concavesurface 134 of the outer sidewall 116 complement the arcuate convexsurface 136 of the inner sidewall 114 and the arcuate convex surface 136of the outer sidewall 116, respectively. That is, in an arrangementincluding more than one steam turbine static nozzle blade 110 (FIGS.5-7), the arcuate convex surface 136 of an inner sidewall 114 of a firststeam turbine static nozzle blade 110 complements the arcuate concavesurface 134 of an inner sidewall 114 on a second similar steam turbinestatic nozzle blade 110. Likewise, the arcuate convex surface 136 of anouter sidewall 116 of a first steam turbine static nozzle blade 110complements the arcuate concave surface 134 of an outer sidewall 116 ona second similar steam turbine static nozzle blade 110. It is understoodthat as used herein, the term “complement(s)” refers to a relationshipbetween surfaces in which portions of those surfaces may be arrangedsubstantially flush with one another. For example, in one embodiment,pressure-side (arcuate concave) surfaces and suction-side (arcuateconvex) surfaces may be arranged in a steam turbine diaphragm assembly(FIG. 7) such that each of the respective (inner, outer) arcuate concavesurfaces of a first steam turbine static nozzle blade 110 aresubstantially flush with the respective (inner, outer) arcuate convexsurfaces of a second steam turbine static nozzle blade 110. Therelationship between pressure-side surfaces and suction-side surfaces isfurther explained with reference to FIGS. 5-7.

Turning to FIGS. 5 and 6, arrangements including a plurality ofsubstantially similar steam turbine static nozzle blades 110 are shown.In these arrangements, steam turbine static nozzle blades 110 may bearranged such that their complementary surfaces (arcuate concavesurfaces 134 and arcuate convex surfaces 136, respectively) aresubstantially flush with one another. This may allow for, among otherthings, efficient feeding of steam across airfoils 112 and mechanicalstability. FIG. 5 shows an arrangement including the plurality of steamturbine static nozzle blades 110 of FIG. 5, along with additionalsubstantially similar blades, forming part of a steam turbine diaphragmassembly (diaphragm rings omitted). As described with respect to FIG. 5,and shown more clearly in FIG. 6, part of a steam turbine diaphragmassembly may be formed by arranging complementary conical surfaces ofsteam turbine static nozzle blades 110 flush with one another. As willbe described with reference to FIG. 7, in a more complete diaphragmassembly, the plurality of steam turbine static nozzle blades 110 may bedemountably attached to one another in an axial direction (denoted by“A”). This demountable attachment may allow for axial removal of one ormore steam turbine static nozzle blades 110 from the assembly withoutsubstantially disturbing the structural integrity (e.g., weld joints190) of the remainder of the assembly.

Turning to FIG. 7, a portion of a steam turbine diaphragm assembly 200is shown according to an embodiment. Portion of steam turbine diaphragmassembly 200 may include a plurality of steam turbine static nozzleblades 110 arranged with substantially flush complementary surfaces asdescribed with reference to FIGS. 5-6. Further, portion of steam turbinediaphragm assembly 200 may include an inner diaphragm ring 118 and anouter diaphragm ring 120, which may be substantially similar to thoseinner and outer rings (18 and 20) shown and described with reference toFIGS. 1-3. In a complete diaphragm assembly (not shown for purposes ofclarity), the plurality of steam turbine static nozzle blades 110 mayform an annulus between the inner diaphragm ring 118 and the outerdiaphragm ring 120. In this arrangement, plurality of steam turbinestatic nozzle blades 110 may be demountably attached to one another.Further, the plurality of steam turbine static nozzle blades 110 may besubstantially removably affixed to at least one of the inner diaphragmring 118 and outer diaphragm ring 120 via the plurality of removableweld joints 190. That is, where a steam turbine static nozzle blade 110is not affixed to at least one of the inner diaphragm ring 118 and outerdiaphragm ring 120, that steam turbine static nozzle blade 110 may beremoved from the steam turbine diaphragm assembly 200 without removingweld joints 190 of one or more adjacent steam turbine static nozzleblades 110.

In the nozzle assembly 100 of FIG. 3, when a complete annulus of staticnozzle blades 10 is assembled and welded (or alternatively, brazed),individual static nozzle blades 10 cannot be removed from the assembly100 without removal of a plurality of the nozzle blades 10 (and theircorresponding weld joints 90, or braze joints). This is because theangled interfaces 34 (FIG. 3) of the plurality of blades 10 obstructmovement of adjacent blades 10, even when a weld joint 90 is removed.Specifically, as shown in FIG. 3, the angled interfaces 34 of theplurality of blades 10 obstruct movement of those blades in an axialdirection (“A”). In contrast, the plurality of steam turbine staticnozzle blades 110 of an embodiment (e.g., FIG. 7) are demountablyattached to one another. That is, each steam turbine static nozzle blade110 that is not welded to one of the inner diaphragm ring 118 and outerdiaphragm ring 120 may be removed or inserted between two fixed (e.g.,welded) steam turbine static nozzle blades 110 in the axial direction(A). Phrased differently, in the steam turbine diaphragm assembly 200,each steam turbine static nozzle blade 110 may be demountably attachedto an adjacent steam turbine static nozzle blade 110 in an axialdirection. Further, in one embodiment each steam turbine static nozzleblade 110 is substantially removably affixed to at least one of theinner diaphragm ring 118 and outer diaphragm ring 120 by only theplurality of removable weld joints 190 (or alternatively, braze joints).

The steam turbine static nozzle blades 110 including conical (arcuateconcave, arcuate convex) interfaces as described herein may allow forremoval of individual blades 110 from an assembly (e.g., steam turbinediaphragm assembly 200) by removing (e.g., by grinding, machining and/orheating) only those removable weld joints 190 (or braze joints)associated with the individual blade being removed. This may allow for,among other things, faster and more efficient repair, replacement,and/or enhancement of individual steam turbine static nozzle blades 110.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A steam turbine static nozzle blade comprising: an airfoil; an innersidewall integral with a first side of the airfoil; and an outersidewall integral with a second side of the airfoil; the inner sidewalland the outer sidewall each including: a pressure side having an arcuateconcave surface extending substantially an entire length of thesidewall; and a suction side having an arcuate convex surface extendingsubstantially the entire length of the sidewall.
 2. The static nozzleblade of claim 1, wherein the arcuate concave surface of the innersidewall and the arcuate convex surface of the inner sidewall have asubstantially equal arc radius.
 3. The static nozzle blade of claim 2,wherein the arcuate concave surface of the outer sidewall and thearcuate convex surface of the outer sidewall have a substantially equalarc radius.
 4. The static nozzle blade of claim 3, wherein the arcuateconcave surface of the inner sidewall and the arcuate concave surface ofthe outer sidewall complement the arcuate convex surface of the innersidewall and the arcuate convex surface of the outer sidewall,respectively.
 5. The static nozzle blade of claim 1, wherein the arcuateconcave surface of the inner sidewall and the arcuate convex surface ofthe inner sidewall have a substantially equal arc length.
 6. The staticnozzle blade of claim 1, wherein the arcuate concave surface of theouter sidewall and the arcuate convex surface of the outer sidewall havea substantially equal arc length.
 7. A steam turbine diaphragm assemblycomprising: an outer diaphragm ring; an inner diaphragm ring; an annulusof static nozzle blades between the inner diaphragm ring and the outerdiaphragm ring, each static nozzle blade comprising: an airfoil; aninner sidewall integral with a first side of the airfoil; and an outersidewall integral with a second side of the airfoil; the inner sidewalland the outer sidewall each including: a pressure side having an arcuateconcave surface extending substantially an entire length of thesidewall; and a trailing surface having an arcuate convex surfaceextending substantially the entire length of the sidewall; wherein atleast one of the static nozzle blades is demountably attached to asecond one of the static nozzle blades.
 8. The steam turbine diaphragmassembly of claim 7, wherein the arcuate concave surface of the innersidewall and the arcuate convex surface of the inner sidewall have asubstantially equal arc radius.
 9. The turbine diaphragm assembly ofclaim 8, wherein the arcuate concave surface of the outer sidewall andthe arcuate convex surface of the outer sidewall have a substantiallyequal arc radius.
 10. The steam turbine diaphragm assembly of claim 9,wherein the arcuate concave surface of the inner sidewall and thearcuate concave surface of the outer sidewall of a first one of thestatic nozzle blades complement the arcuate convex surface of the innersidewall and the arcuate convex surface of the outer sidewall,respectively, of a second one of the static nozzle blades.
 11. The steamturbine diaphragm assembly of claim 10, further comprising a pluralityof removable weld joints, each removable weld joint substantiallyremovably affixing one of the static nozzle blades to one of the outerdiaphragm ring or the inner diaphragm ring.
 12. The steam turbinediaphragm assembly of claim 11, wherein the at least one of the staticnozzle blades is demountably attached to the second one of the staticnozzle blades by at least one of the removable weld joints.
 13. Thesteam turbine diaphragm assembly of claim 12, wherein the at least oneof the removable weld joints demountably attaches the at least one ofthe static nozzle blades to the second one of the static nozzle bladesin an axial direction.
 14. A steam turbine diaphragm assemblycomprising: an outer diaphragm ring; an inner diaphragm ring; an annulusof static nozzle blades between the inner diaphragm ring and the outerdiaphragm ring, each static nozzle blade comprising: an airfoil; aninner sidewall integral with a first side of the airfoil; and an outersidewall integral with a second side of the airfoil; the inner sidewalland the outer sidewall each including: a pressure side having an arcuateconcave surface extending substantially an entire length of thesidewall; and a suction side having an arcuate convex surface extendingsubstantially the entire length of the sidewall, wherein at least one ofthe static nozzle blades is demountably attached to a second one of thestatic nozzle blades in an axial direction; and a plurality of pairs ofremovable weld joints, each pair of removable weld joints substantiallyremovably affixing one of the static nozzle blades to one of the outerdiaphragm ring or the inner diaphragm ring.
 15. The steam turbinediaphragm assembly of claim 14, wherein the arcuate concave surface ofthe inner sidewall and the arcuate convex surface of the inner sidewallhave a substantially equal arc radius.
 16. The steam turbine diaphragmassembly of claim 15, wherein the arcuate concave surface of the outersidewall and the arcuate convex surface of the outer sidewall have asubstantially equal arc radius.
 17. The steam turbine diaphragm assemblyof claim 15, wherein the arcuate concave surface of the inner sidewalland the arcuate concave surface of the outer sidewall of a first one ofthe static nozzle blades complement the arcuate convex surface of theinner sidewall and the arcuate convex surface of the outer sidewall,respectively, of a second one of the static nozzle blades.
 18. The steamturbine diaphragm assembly of claim 14, wherein each pair of removableweld joints substantially maintains an axial position of the removablyaffixed static nozzle blade.
 19. The steam turbine diaphragm assembly ofclaim 14, wherein the arcuate concave surface of the inner sidewall andthe arcuate convex surface of the inner sidewall have a substantiallyequal arc length; and wherein the arcuate concave surface of the outersidewall and the arcuate convex surface of the outer sidewall have asubstantially equal arc length.
 20. The steam turbine diaphragm assemblyof claim 14, wherein the removably affixed static nozzle blade issubstantially affixed to the turbine diaphragm assembly by only the pairof removable weld joints.